Endometriosis Mimicking an Advanced Malignant Tumor.

A 27-year-old woman with swelling left leg, groin pain, and increased serum CA125 level underwent FDG PET/CT to evaluate a pelvic mass revealed by an MRI performed from an outside hospital. A large hypermetabolic solid mass in the left pelvic wall and several lymph nodes with elevated FDG activity were noted, which indicated malignancy. However, histopathological examination demonstrated endometriosis.